Lithographic microfabrication using a photoresist composition has been employed in processes for producing semiconductor devices such as ICs and LSIs. Due to increased integration of integrated circuit boards in recent years, super-micro patterns in the order of submicron or quarter micron are being demanded. Along with this tendency, the wavelength of radiation used for exposure tends to be shortened to g-lines, and i-lines, and further to a KrF excimer laser. At the present time, in addition to the lithographic process using excimer lasers, lithographic processes using electron beams, X-rays, or EUV-rays are being developed.
Electron beam lithography is particularly expected as a pattern forming technology of the next generation or the next-next generation. Development of a positive-tone resist exhibiting high sensitivity and high resolution is also desired. Increasing the sensitivity is very important in order to reduce the time required for wafer processing. However, increasing sensitivity of a positive-tone resist for use with electron beams not only decreases resolution, but also tends to cause line edge roughness. For this reason, development of a resist which can satisfy properties such as sensitivity, resolution, and line edge roughness at the same time is strongly desired.
The line edge roughness refers to roughness of the edge on the interface of the resist pattern and the substrate. That is, the edge on the interface of the resist pattern and the substrate irregularly fluctuates in the direction vertical to the line direction due to the properties of the resist. When the pattern is viewed from directly above, the edge is seen to have irregularity. Since the irregularity is transferred in the etching step in which the resist is used as a mask, the electrical properties deteriorate and the yield is decreased. Improvement of line edge roughness is very important particularly in a ultra-micro region of 0.25 μm or less. High sensitivity, high resolution, good pattern form, and good line edge roughness are in a trade-off relationship, and satisfying these properties at the same time is a very important subject. Satisfying high sensitivity, high resolution, and the like is also very important also in lithography using X-rays and EUV-rays.
As a resist suitable for a lithography process using electron beams, X-rays, or EUV-rays, chemically amplified resists which mainly use an acidic catalyst reaction are used from the viewpoint of high sensitivity. In a positive-tone resist, a chemically-amplified resist composition containing a phenolic polymer, which is insoluble or scarcely soluble but becomes soluble in an alkaline aqueous solution by the action of an acid (acid-dissociable phenolic resin), and an acid generator as main components is effectively used.
As such an acid-dissociable phenolic resin, a phenol compound derivative having a specific structure (Patent Documents 1 to 3), a calixarene having a specific structure (Patent Documents 4 and 5), a calix resorcin arene (Patent Documents 5 and 6), a phenolic dendrimer having a calix resorcin arene as a mother nucleus (Patent Document 7), and the like have been disclosed. Resist compositions in which these compounds are used have also been disclosed.
However, no combination of the above-described resins has been successful in achieving high sensitivity, high resolution, good pattern form, and good line edge roughness at the same time.    Patent Document 1: JP-A-10-83073    Patent Document 2: JP-A-2000-305270    Patent Document 3: JP-A-2003-183227    Patent Document 4: JP-A-10-120610    Patent Document 5: JP-A-11-322656    Patent Document 6: JP-A-2003-321423    Patent Document 7: JP-A-10-310545